Electric-power conversion apparatus

ABSTRACT

A control unit of an electric-power conversion apparatus has an input current amplitude command value creation means that creates an input current amplitude command value, which is an amplitude command value of an input current of a first electric-power conversion circuit, in accordance with an output current command value, which is a command value of an output current of a second electric-power conversion circuit, when the output current command value changes; the control unit controls the first electric-power conversion circuit so that an input current follows an input current command value created based on an input current amplitude command value created by the input current amplitude command value creation means; the control unit controls the second electric-power conversion circuit so that an output current follows an output current command value.

BACKGROUND OF THE INVENTION Field of the Invention

The present disclosure relates to an electric-power conversionapparatus.

Description of the Related Art

As an example of an electric-power conversion apparatus that convertsthe voltage and the current of a power source into those of desiredvalues and supplies the converted voltage and current to a load, thereexists an electric-power conversion apparatus including

a first electric-power conversion circuit that receives AC electricpower of a power source, as an input, and then performs electric-powerconversion between the AC electric power and DC electric power whileimproving the input power factor,

a smoothing capacitor connected with the output side of the firstelectric-power conversion circuit,

a second electric-power conversion circuit that converts DC electricpower supplied to the smoothing capacitor by the first electric-powerconversion circuit into AC electric power and then supplies the ACelectric power to the load, and

a control unit that makes the second electric-power conversion circuitoperate to supply desired electric power to the load, while making thefirst electric-power conversion circuit operate so that the voltageacross the smoothing capacitor becomes a desired voltage while the inputpower factor is improved.

The control unit of this kind of an electric-power conversion apparatusis configured in such a way that when the value of a current to besupplied to a load such as a battery is changed, the secondelectric-power conversion circuit is made to operate to graduallyincrease an output current command value to a desired current value sothat when electric power is supplied to the load, the load is preventedfrom failing due to a sudden increase in the electric power. In thissituation, the control unit operates an input current amplitude commandvalue of the first electric-power conversion circuit so that the voltageacross the smoothing capacitor follows the output current command value.That is to say, after due to a gradual increase in the output currentcommand value, electric power is supplied from the smoothing capacitorto the load and hence the voltage across the smoothing capacitordecreases, the input current amplitude command value is operated.Accordingly, a delay in the operation control makes the increasing speedof input electric power of the electric-power conversion apparatus lowerthan a desired increasing speed of output electric power.

As described above, while the output current command value changes insuch a manner as a gradual increase, the changing amount of a desiredoutput electric power is large; thus, there occurs a time period inwhich the amount of input electric power does not reach the amountcorresponding to desired output electric power and hence it requirestime until the control unit performs control so as to obtain a desiredinput/output electric power condition and a steady state is realized. Asa result, in the case where the load is, for example, a battery, thecharging time is prolonged.

In order to improve such a response delay in the input electric power asdescribed above at a time when the output current command value changes,for example, in a conventional electric-power conversion apparatusdisclosed in Patent Document 1, based on an output current command valueof a second electric-power converter, the input electric power and theDC input current of the second electric-power converter are estimatedthrough a calculation considering the changing rate of the outputcurrent command value; the AC input current value of a firstelectric-power converter is calculated based on the estimation values;the AC input current value of the first electric-power converter iscontrolled in accordance with the calculation value, so that the inputelectric power and the output electric power of the electric-powerconversion apparatus are made to coincide with each other while theoutput current command value changes; as a result, the voltage acrossthe smoothing capacitor is suppressed from changing, so that theresponse delay caused by a control delay is improved.

PRIOR ART REFERENCE Patent Literature

[Patent Document 1] Japanese Patent No. 3381465

SUMMARY OF THE INVENTION

In the conventional electric-power conversion apparatus disclosed inPatent Document 1, it is required that in order to estimate the DC inputcurrent of the second electric-power converter through a calculationconsidering the changing rate of the output current command value, thevoltage across the smoothing capacitor is detected and then the DC inputcurrent of the second electric-power converter is estimated by use ofthe detection value. Accordingly, a control delay occurs due to, forexample, the fact that it is required that the voltage across thesmoothing capacitor is detected and A/D conversion processing is appliedto the detection value. That is to say, because the voltage value of thesmoothing capacitor to be utilized in the foregoing estimationcalculation includes a control delay, there occurs a control delay untilthe control unit performs control so as to establish a desiredinput/output condition; thus, the voltage across the smoothing capacitorchanges.

As described above, in the conventional electric-power conversionapparatus that converts the voltage and the current of a power sourceinto desired values and then supplies those of the desired values to aload, because the voltage value of the smoothing capacitor is utilizedin a calculation, there still occurs a discrepancy between the inputelectric power, operated by the control unit, and the output electricpower of the electric-power conversion apparatus; therefore, there hasbeen a problem that it requires time until the control unit controls thefirst and second electric-power conversion circuits so as to obtain adesired input/output electric power condition and the operation becomessteady.

The present disclosure has been implemented in order to solve theforegoing problem; the objective thereof is to provide an electric-powerconversion apparatus that improves a control delay and realizesreduction of the time until the control becomes steady.

An electric-power conversion apparatus disclosed in the presentdisclosure includes

a first electric-power conversion circuit that converts electric powerof a power source supplied from an input side thereof into firstelectric power and then outputs the first electric power from an outputside thereof,

a smoothing capacitor connected with the output side of the firstelectric-power conversion circuit,

a second electric-power conversion circuit that converts electric powerinputted to an input side thereof by way of the smoothing capacitor intosecond electric power and then supplies electric power based on thesecond electric power to a load connected with an output side thereof,and

a control unit that controls the first electric-power conversion circuitand the second electric-power conversion circuit so that a voltageacross the smoothing capacitor follows a voltage target value.

The electric-power conversion apparatus is characterized

in that the control unit has an input current amplitude command valuecreation means that creates an input current amplitude command value,which is an amplitude command value of an input current of the firstelectric-power conversion circuit, in accordance with an output currentcommand value, which is a command value of an output current of thesecond electric-power conversion circuit, when the output currentcommand value changes,

in that based on the input current amplitude command value created bythe input current amplitude command value creation means, the controlunit creates an input current command value, which is a command value ofan input current of the first electric-power conversion circuit,

in that the control unit controls the first electric-power conversioncircuit so that an input current of the first electric-power conversioncircuit follows the input current command value, and

in that the control unit controls the second electric-power conversioncircuit so that an output current of the second electric-powerconversion circuit follows the output current command value.

An electric-power conversion apparatus disclosed in the presentdisclosure improves a control delay and realizes reduction of the timeuntil the control becomes steady.

The foregoing and other object, features, aspects, and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram representing the configuration of anelectric-power conversion apparatus according to any one of Embodiments1 through 3;

FIG. 2 is a functional configuration diagram for explaining theoperation of the electric-power conversion apparatus according to anyone of Embodiments 1 through 3;

FIG. 3 is a set of waveform charts for explaining the operation of afirst electric-power conversion circuit in the electric-power conversionapparatus according to Embodiment 1;

FIG. 4 is an explanatory diagram for explaining the operation of asecond electric-power conversion circuit in the electric-powerconversion apparatus according to Embodiment 1;

FIG. 5 is a set of waveform charts for explaining the operation of thefirst electric-power conversion circuit in an electric-power conversionapparatus according to Embodiment 2;

FIG. 6 is a set of waveform charts for explaining the operation of thefirst electric-power conversion circuit in an electric-power conversionapparatus according to Embodiment 3; and

FIG. 7 is an explanatory diagram for explaining the operation of asecond electric-power conversion circuit in the electric-powerconversion apparatus according to Embodiment 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, respective electric-power conversion apparatuses accordingto Embodiments 1 through 3 of the present disclosure will be explainedbased on the drawings.

Embodiment 1

FIG. 1 is a configuration diagram representing the configuration of anelectric-power conversion apparatus according to any one of Embodiments1 through 3. In FIG. 1, an electric-power conversion apparatus 1000 isprovided with

a first electric-power conversion circuit 100 whose input side isconnected with an AC power source 1 and whose output side is connectedwith a smoothing capacitor 2,

a second electric-power conversion circuit 200 whose input side isconnected with the smoothing capacitor 2 and whose output side isconnected with a high-voltage battery 3, as a load, and

a control unit 4 that controls the first electric-power conversioncircuit 100 and the second electric-power conversion circuit 200. Thefirst electric-power conversion circuit 100 converts electric power of apower source, inputted from the input side, into first electric powerand then outputs the first electric power from the output side. Thesecond electric-power conversion circuit 200 converts electric power,inputted to the input side thereof by way of the smoothing capacitor 2,into second electric power and then supplies electric power based on thesecond electric power to the load connected with the output sidethereof. In Embodiment 1, there is described an example in which thepower source is an AC power source, the first electric power is DCelectric power, and the second electric power is AC electric power;however, the present disclosure is not limited thereto.

The first electric-power conversion circuit 100 is a circuit thatperforms electric-power conversion through switching operation by asemiconductor switching device 7; the second electric-power conversioncircuit 200 is a circuit that performs electric-power conversion throughswitching operational actions by semiconductor switching devices 9, 10,11, and 12. As described later, a detection circuit for detecting acurrent and a voltage is mounted at a predetermined position in each ofthe first electric-power conversion circuit 100 and the secondelectric-power conversion circuit 200; these detection circuits transferdetected current values and voltage values to the control unit 4. Basedon a charging target value Iout_ref to be inputted thereto from anexternal charging target value transmitter 2000, the control unit 4creates an input current command value and an output current commandvalue, as current command values, and PWM (Pulse WidthModulation)-controls the semiconductor switching device 7 of the firstelectric-power conversion circuit 100 and the semiconductor switchingdevices 9, 10, 11, and 12 of the second electric-power conversioncircuit 200 so that the detected current values follow the currentcommand values. In this situation, the control unit 4 creates the outputcurrent command value in such a way that the immediately previouslycreated output current command value (the initial value thereof is “0”)gradually increases or gradually decreases for the charging target valueIout_ref and then reaches the charging target value Iout_ref.

Each of the semiconductor switching device 7 of the first electric-powerconversion circuit 100 and the semiconductor switching devices 9, 10,11, and 12 of the second electric-power conversion circuit 200 is formedof, for example, a MOSFET (Metal Oxide Semiconductor Field EffectTransistor) containing a diode between the source and the drain thereof.

The first electric-power conversion circuit 100 includes elements fromthe AC power source 1, as an AC input power source, to the smoothingcapacitor 2. A diode bridge 5, as a rectification circuit, is connectedwith the AC power source 1 by way of an input current detection circuit21. An input voltage detection circuit 20 is connected in parallel withthe diode bridge 5 at the input side of the diode bridge 5. A reactor 6,as a current limiting circuit, is connected with the output side of thediode bridge 5.

The post-stage of the reactor 6 is connected with one end of thesemiconductor switching device 7 and the anode of a rectifier diode 8.The cathode of the rectifier diode 8 is connected with the positiveelectrode of the smoothing capacitor 2 connected with the output side ofthe first electric-power conversion circuit 100. The other end of thesemiconductor switching device 7 connected with the post-stage of thereactor 6 is connected with the negative electrode of the smoothingcapacitor 2. A DC voltage detection circuit 22 for detecting the voltageacross the smoothing capacitor 2 is connected in parallel with thesmoothing capacitor 2

The second electric-power conversion circuit 200 includes elements fromthe smoothing capacitor 2 to the high-voltage battery 3, as a load. Theinput side of a bridge circuit including the four semiconductorswitching devices 9, 10, 11, and 12 is connected across the smoothingcapacitor 2. The respective drains of the semiconductor switchingdevices 9 and 11 are connected with the positive-electrode of thesmoothing capacitor 2; the respective sources of the semiconductorswitching devices 10 and 12 are connected with the negative-electrode ofthe smoothing capacitor 2.

One end of a primary winding 131 of a transformer 13 is connected withthe connection point between the source of the semiconductor switchingdevice 9 and the drain of the semiconductor switching device 10; theother end of the primary winding 131 of the transformer 13 is connectedwith the connection point between the source of the semiconductorswitching device 11 and the drain of the semiconductor switching device12. A secondary winding 132 of the transformer 13 is connected with theinput side of a rectification circuit formed of a full-bridge circuitincluding four rectifier diodes 14, 15, 16, and 17. A smoothing reactor18, an output current detection circuit 23, and a smoothing capacitor 19are connected with the output side of the rectification circuitincluding the rectifier diodes 14, 15, 16, and 17. An output voltagedetection circuit 24 is connected in parallel with the smoothingcapacitor 19. The high-voltage battery 3, as a load, is connected withthe output side of the second electric-power conversion circuit 200.

Next, the operation of the first electric-power conversion circuit 100will be explained. FIG. 2 is a functional configuration diagram forexplaining the operation of the electric-power conversion apparatusaccording to any one of Embodiments 1 through 3. At first, the operationat a time when the output current command value is not graduallyincreasing or not gradually decreasing will be explained. In FIGS. 1 and2, in accordance with an output voltage Vout of the electric-powerconversion apparatus 1000, the control unit 4 of the electric-powerconversion apparatus 1000 adjusts a voltage target value Vdc* of thesmoothing capacitor 2 so that the second electric-power conversioncircuit 200 operates in a high-efficiency manner. Then, in an inputcurrent amplitude command value creation means 50 included in thecontrol unit 4, an output current command value change determinationunit 51 determines and detects a change in an output current commandvalue Iout*.

In the case where a determination by the output current command valuechange determination unit 51 does not detect any change in the outputcurrent command value Iout*, the input current amplitude command valuecreation means 50 outputs a value obtained by applying proportionalintegral (PI) control to a difference 31 between a DC voltage Vdcdetected by the DC voltage detection circuit 22 and the voltage targetvalue Vdc* of the smoothing capacitor 2, as an input current amplitudecommand value IinAMP* of the electric-power conversion apparatus 1000.The control unit 4 creates an input current command value Iin* based onthe input current amplitude command value IinAMP* and an AC power sourcesynchronization sinusoidal wave 33, created as a signal having anamplitude of “1”, which is synchronized with an input voltage Vindetected by the input voltage detection circuit 20.

Next, a value obtained by applying proportional integral (PI) control toa difference 35, as a feedback amount, between the input current commandvalue Iin* and an input current Iin is provided, as a target voltageVLin which is a target value as a voltage to be applied to the reactor6, to a gate signal generator 60 included in the control unit 4.

In this situation, when the semiconductor switching device 7 operates atan arbitrary duty ratio D1, the relationship among the input voltageVin, the DC voltage Vdc of the smoothing capacitor 2, and the targetvoltage VLin is represented by the equation below for one switchingperiod of the semiconductor switching device 7.

Vin=VLin+Vdc(1−D1)

The gate signal generator 60 calculates the duty ratio D1 based on thefollowing equation obtained from the foregoing equation and outputs agate signal 37 to the semiconductor switching device 7 so that thesemiconductor switching device 7 is PWM-controlled based on thecalculated duty ratio D1.

D1=1−(Vin−VLin)/Vdc

Next, there will be explained the operation of the input currentamplitude command value creation means 50 at a time when theelectric-power conversion apparatus 1000 starts its electric-powerconversion operation and the output current command value Iout* isincreasing. FIG. 3 is a set of waveform charts for explaining theoperation of the first electric-power conversion circuit in theelectric-power conversion apparatus according to Embodiment 1; theordinate denotes the output current, the output-current difference, andthe input current, and the abscissa denotes the time t.

In the time period where t<t1 in FIG. 3, the output current commandvalue change determination unit 51 in the input current amplitudecommand value creation means 50 detects a change in the output currentcommand value Iout* after the electric-power conversion operation hasbeen started and determines

whether or not the absolute value (equal to the instantaneous value ofthe Iout*, in Embodiment 1) of a changing amount of the output currentcommand value Iout* from the value (“0”, in Embodiment 1) of the outputcurrent command value Iout* at a time prior to the start of gradualincrease is larger than “0” and smaller than a threshold value Iout*_ththat is smaller than the absolute value (equal to the charging targetvalue, in Embodiment 1) of the difference between the output currentcommand value Iout* (“0”, in Embodiment 1) at a time prior to the startof gradual increase and the charging target value Iout_ref or

whether or not the absolute value Idiff of the difference between theoutput current command value Iout* and an output current lout is largerthan “0” and larger than a threshold value Idiff th that is smaller thanthe absolute value (equal to the charging target value, in Embodiment 1)of the difference between the output current command value Iout* (“0”,in Embodiment 1) at a time prior to the start of gradual increase andthe charging target value Iout_ref.

The condition in this case is given by the following equation.

|Iout*−Iout*at a time prior to the start of gradual increae|<Iout*_th

where 0<Iout*_th<|charging target value−Iout* at a time prior to thestart of gradual increase|

or

|Iout*−Iout|=Idiff>Idiff_th

where 0<Idiff_th<|charging target value−Iout*at a time prior to thestart of gradual increase|.

In this situation, as represented in FIG. 2, the multiplier 52 in theinput current amplitude command value creation means 50 calculates andoutputs the multiplication product of the output current command valueIout* and the output voltage Vout detected by the output voltagedetection circuit 24. That is to say, the output of the multiplier 52indicates output electric power Pout at the output current command valueIout*. Then, as the input current amplitude command value IinAMP*, thereis outputted a value, given by the equation below, that is obtained bydividing, through the divider 53, the output electric power Pout by aninput voltage amplitude VinAMP detected from the input voltage Vin bythe control unit 4 and the electric-power conversion efficiency, of theelectric-power conversion apparatus 1000, that is preliminarily storedin the input current amplitude command value creation means 50 and isbased on the condition determined by the output electric power Pout andthe input voltage amplitude VinAMP.

IinAMP*=(Iout*×Vout)/(VinAMP×electric-power conversion efficiency)

In this situation, the input current amplitude command value creationmeans 50 stops the processing of applying proportional integral (PI)control to the difference 31 between the voltage target value Vdc* andthe DC voltage Vdc and then resets the output value of the proportionalintegral (PI) control.

The following operation until the gate signal generator 60 outputs thegate signal 37 to the semiconductor switching device 7 is the same asthat at a time when the output current command value Iout* is notgradually increasing or not gradually decreasing.

As described above, in the electric-power conversion apparatus 1000according to Embodiment 1, it is not required that when the inputcurrent amplitude command value IinAMP* is created, the input currentamplitude command value creation means 50 utilizes the DC voltage Vdc ofthe smoothing capacitor 2 detected by the DC voltage detection circuit22. In other words, because the input current amplitude command valueIinAMP* is created based on the output voltage Vout, which is thevoltage of the high-voltage battery 3, as a load, and whose temporalchange is small, the input voltage amplitude VinAMP, which is suppliedfrom an electric-power system and is detected from the input voltageVin, the present output current command value Iout*, and theelectric-power conversion efficiency, which is a constant, the effect ofa control delay, caused, for example, by detecting the DC voltage Vdcand AD-converting the detection value, can be eliminated.

Accordingly, the input current amplitude command value IinAMP*, which isnecessary for the output current lout to follow the output currentcommand value Iout*, is appropriately created, so that the DC voltageVdc of the smoothing capacitor 2 can be suppressed from decreasing andhence the time until the electric-power supplying operation becomessteady can be shortened. Furthermore, the time for charging thehigh-voltage battery 3 can be shortened.

Next, in the time period where t≥t1 in FIG. 3, the output currentcommand value change determination unit 51 in the input currentamplitude command value creation means 50 detects a change in the outputcurrent command value Iout* and determines whether or not the absolutevalue (equal to the instantaneous value of the Iout*, in Embodiment 1)of a changing amount of the output current command value Iout* from thevalue (“0”, in Embodiment 1) of the output current command value Iout*at a time prior to the start of gradual increase is the same as orlarger than the threshold value Iout*_th and the absolute value Idiff ofthe difference between the output current command value Iout* and theoutput current lout is the same as or smaller than Idiff_th. Thecondition in this case is given by the following equation.

|Iout*−Iout* at a time prior to the start of gradual increase|≥Iout*_th

and

Idiff≤Idiff_th

In this situation, the input current amplitude command value creationmeans 50 outputs, as the initial value, the input current amplitudecommand value IinAMP* created immediately before the condition [t≥t1] isestablished; after that, as is the case with the control at a time whenthe output current command value Iout* is not gradually increasing ornot gradually decreasing, the input current amplitude command valuecreation means 50 applies proportional integral (PI) control to thedifference 31 between the DC voltage Vdc and the voltage target valueVdc* and then outputs the output, as the input current amplitude commandvalue IinAMP*. The following control until the gate signal 37 isoutputted to the semiconductor switching device 7 is the same as that ata time when the output current command value Iout* is not graduallyincreasing or not gradually decreasing. As a result, it is made possiblethat even after the operation of the electric-power conversion apparatus1000 has become steady, the voltage of the smoothing capacitor 2 and theinput and output currents of the electric-power conversion apparatus1000 are stably controlled.

Next, the control of the second electric-power conversion circuit 200will be explained. FIG. 4 is an explanatory diagram for explaining theoperation of the second electric-power conversion circuit in theelectric-power conversion apparatus according to Embodiment 1. Thecontrol unit 4 generates an output 43 obtained by applying proportionalintegral (PI) control to a difference 42, as a feedback amount, betweenthe output current command value Iout* and the output current loutdetected by the output current detection circuit 23. The output 43corresponds to a target voltage VLout, which is a target value, as thevoltage to be applied to the smoothing reactor 18.

Next, when the semiconductor switching devices 9, 10, 11, and 12 areeach controlled with a duty ratio D2, the relationship among the outputvoltage Vout detected by the output voltage detection circuit 24, the DCvoltage Vdc, and the target voltage VLout is given by the equation belowfor one switching period of each of the semiconductor switching devices9, 10, 11, and 12, letting N1 and N2 denote the number of turns of theprimary winding 131 of the transformer 13 and the number of turns of thesecondary winding 132 thereof, respectively.

Vout=N2/N1·Vdc·D2−VLout

As a result, based on the equation given below, the gate signalgenerator 60 calculates the duty ratio D2 and then outputs gate signals44, 45, 46, and 47 for performing PWM control based on the duty ratio D2to the semiconductor switching devices 9, 10, 11, and 12, respectively.

D2=N1/N2 (Vout+VLout)/Vdc

The gate signal 44 is provided to the semiconductor switching device 9;the gate signal 45 is provided to the semiconductor switching device 10;the gate signal 46 is provided to the semiconductor switching device 11;the gate signal 47 is provided to the semiconductor switching device 12.

As described above, because without utilizing the value of the DCvoltage of the smoothing capacitor 2, the input current amplitudecommand value IinAMP* is created in accordance with the output currentcommand value Iout* and the output and input currents are controlled soas to follow those command values, there occurs no calculation delaycaused by utilizing the voltage value of the smoothing capacitor 2 inthe calculation; therefore, it is made possible that the voltage of thesmoothing capacitor 2 is suppressed from decreasing, that there isimproved a control delay at a time when the control unit 4 makes theelectric-power conversion apparatus 1000 operate under a desiredinput/output electric-power condition, and that the time until theelectric-power supplying operation becomes steady is shortened.

In the first electric-power conversion circuit 100 having an operationmode where the output current lout of the second electric-powerconversion circuit 200 is made to follow the output current commandvalue Iout* and the input current amplitude command value IinAMP*thereof is created so as to control the DC voltage Vdc of the smoothingcapacitor 2, it is required that the control unit 4 appropriatelychanges the input current amplitude command value IinAMP* in accordancewith a change in the output current command value Iout*. In theforegoing electric-power conversion apparatus 1000 according toEmbodiment 1, because the input current amplitude command value creationmeans 50 creates the input current amplitude command value IinAMP* inaccordance with a change in the output current command value Iout*, itis made possible to make the input current amplitude command valueIinAMP* appropriately change in accordance with a change in the outputcurrent command value Iout*; thus, it is useful in particular.

In Embodiment 1, the control unit 4 includes a controller such as amicrocomputer that performs processing in a predetermined period. Inthis situation, the control unit 4 controls the input current Iin so asto apply power factor control to the AC input voltage Vin to be inputtedfrom the AC power source 1. Accordingly, it is required to keep thesinusoidal-wave amplitude of the input current Iin at a constant valueduring one AC period of the input voltage Vin; thus, it is required toapply creation processing to the input current amplitude command valueIinAMP* in synchronization with the AC period T1 of the input voltageVin. Therefore, in comparison with a creation-processing period T2 ofthe output current command value Iout* that gradually increases orgradually decreases without undergoing these restrictions, the creationperiod of the input current amplitude command value IinAMP* becomeslong.

Accordingly, when the control in the electric-power conversion apparatus1000 according to Embodiment 1 is not applied, a delay in controllingthe input current amplitude command value IinAMP* makes the voltageacross the smoothing capacitor 2 conspicuously change; however, when thecontrol in the electric-power conversion apparatus 1000 according toEmbodiment 1 is applied, the voltage across the smoothing capacitor 2can be suppressed from decreasing, without a calculation delay caused byutilizing the voltage value of the smoothing capacitor 2 in thecalculation. That is to say, in the electric-power conversion apparatus1000 according to Embodiment 1, it is made possible that a control delayat a time when the control unit 4 makes the electric-power conversionapparatus 1000 operate with a desired input/output electric powercondition is improved and hence the time until the operation becomessteady for stable electric-power supply is shortened.

Moreover, because when the electric-power conversion apparatus 1000 isstarted, the output current command value Iout* is created in such a wayas to gradually increase from a state of “0” for the charging targetvalue Iout_ref, application of the foregoing control at a starting timeprovides an effect that especially, the control delay is improved andhence the time until the operation becomes steady for stableelectric-power supply can be shortened.

In Embodiment 1, there has been described that the input currentamplitude command value creation means 50 stores the electric-powerconversion efficiencies, of the electric-power conversion apparatus1000, that are determined by the conditions of the output electric powerPout and the input voltage amplitude VinAMP; however, it may be allowedthat only the lowest one of the electric-power conversion efficienciesunder the conditions is stored and is always utilized. As a result, theinput current amplitude command value IinAMP* is created based on theassumption that the value of the electric-power conversion efficiency ofthe electric-power conversion apparatus 1000 is lowest. Accordingly,depending on the condition, the input electric power becomes large forthe output electric power Pout and hence the voltage across thesmoothing capacitor 2 can rise; however, because in order to satisfy thewithstanding voltage specification of the smoothing capacitor 2, thiskind of electric-power conversion apparatus has control for protectingthe smoothing capacitor 2 from the voltage rise, it is made possible toobtain an effect the same as that described above, without causing thesmoothing capacitor 2 to fail.

Embodiment 2

Next, an electric-power conversion apparatus according to Embodiment 2will be explained. The configuration of the electric-power conversionapparatus according to Embodiment 2 is the same as that of Embodiment 1,represented in FIGS. 1 and 2. In the control by the control unit 4 andthe input current amplitude command value creation means 50 according toEmbodiment 2, the control at a time when the output current commandvalue is not gradually increasing or not gradually decreasing is thesame as that in Embodiment 1.

FIG. 5 is a set of waveform charts for explaining the operation of theelectric-power conversion apparatus according to Embodiment 2; theordinate denotes the output current, the output-current difference, theDC voltage, and the input current, and the abscissa denotes the time t.By use of FIG. 5, there will be explained the operation of the inputcurrent amplitude command value creation means 50 at a time when after afirst charging target value Iout_ref1 has been inputted to the controlunit 4 and then a second charging target value Iout_ref2 is inputted tothe control unit 4, the output current command value Iout* is graduallyincreasing.

After the first charging target value Iout_ref1 represented in FIG. 5 isinputted to the control unit 4 till the time instant t2, the secondcharging target value Iout_ref2 is inputted thereto at the time instantt2; then, the control unit 4 gradually increases the output currentcommand value Iout* from the first charging target value Iout_ref1 tothe second charging target value Iout_ref2. In this situation, in thetime period of [t2≤t<t3] in FIG. 5, the output current command valuechange determination unit 51 in the input current amplitude commandvalue creation means 50 detects a change in the output current commandvalue Iout* and determines that the absolute value Idiff of thedifference between the output current command value Iout* and the outputcurrent lout is larger than “0” and smaller than a threshold valueIdiff_th2 that is smaller than the absolute value (|the second chargingtarget value Iout_ref2—the output current command value Iout* at a timebefore it starts to gradually increase|) of the difference between theoutput current command value Iout* at a time before it starts togradually increase (equal to the first charging target value Iout_ref1,in Embodiment 21) and the second charging target value Iout_ref2. Thecondition in this case is given by the following equation.

Idiff<Idiff_th2

where 0<Idiff_th2<|second charging target value Iout_ref2—the outputcurrent command value Iout* at a time before it starts to graduallyincrease|.

In this situation, the input current amplitude command value creationmeans 50 performs control the same as that at a time when the outputcurrent command value Iout* is not gradually increasing or not graduallydecreasing. The operation of the control unit 4 is the same as that at atime when the output current command value Iout* is not graduallyincreasing or not gradually decreasing.

Next, in the time period of [t3≤t<t4] in FIG. 5, the output currentcommand value change determination unit 51 in the input currentamplitude command value creation means 50 detects a change in the outputcurrent command value Iout* and determines whether or not the absolutevalue Idiff of the difference between the output current command valueIout* and the output current lout is the same as or larger than thethreshold value Idiff_th2 and the DC voltage Vdc is smaller than athreshold value Vdc_th that is larger than the voltage target valueVdc*. The condition in this case is given by the following equation.

Idiff≥Idiff_th2

and

Vdc<Vdc_th

where Vdc_th>Vdc*.

In this situation, as represented in FIG. 2, the multiplier 52 in theinput current amplitude command value creation means 50 calculates andoutputs the multiplication product of the output current command valueIout* and the output voltage Vout detected by the output voltagedetection circuit 24. That is to say, the output of the multiplier 52indicates the output electric power Pout at the output current commandvalue Iout*. Then, as the input current amplitude command value IinAMP*,there is outputted a value, given by the equation below, that isobtained by dividing, through the divider 53, the output electric powerPout by the input voltage amplitude VinAMP detected from the inputvoltage Vin by the control unit 4 and the electric-power conversionefficiency preliminarily stored in the input current amplitude commandvalue creation means 50.

IinAMP*=(Iout*×Vout)/(VinAMP×the electric-power conversion efficiency)

In this situation, the input current amplitude command value creationmeans 50 stops the processing of applying proportional integral (PI)control to the difference 31 between the voltage target value Vdc* andthe DC voltage Vdc and then resets the output value of the proportionalintegral (PI) control. The following control until the gate signal 37 isoutputted to the semiconductor switching device 7 is the same as that ata time when the output current command value is not gradually increasingor not gradually decreasing.

As described above, in the electric-power conversion apparatus 1000according to Embodiment 2, it is not required that in the calculationfor creating the input current amplitude command value IinAMP*, theinput current amplitude command value creation means 50 utilizes the DCvoltage Vdc of the smoothing capacitor 2 detected by the DC voltagedetection circuit 22. In other words, because the input currentamplitude command value IinAMP* is created based on the output voltageVout, which is equal to the voltage of the high-voltage battery 3 andwhose temporal change is small, the input voltage amplitude VinAMP,which is supplied from an electric-power system, the present outputcurrent command value Iout*, and the electric-power conversionefficiency, which is a constant, the effect of a control delay, caused,for example, by detecting the DC voltage Vdc and AD-converting thedetection value, can be eliminated.

Therefore, because the input current amplitude command value IinAMP*that is necessary for the output current lout to follow the outputcurrent command value Iout* is appropriately created, it is madepossible to suppress the voltage of the smoothing capacitor 2 fromdecreasing, to shorten the time until the electric-power supplyingoperation becomes steady, and to shorten the time for charging thehigh-voltage battery 3.

Next, in the time period where t4≤t in FIG. 5, the output currentcommand value change determination unit 51 detects a change in theoutput current command value Iout* and determines that the DC voltageVdc is the same as or larger than the threshold value Vdc_th. Thecondition in this case is given by the following equation.

Vdc≥Vdc_th

In this situation, the input current amplitude command value creationmeans 50 outputs, as the initial value, the input current amplitudecommand value IinAMP* created immediately before [t≥t4] is established;as is the case with the control at a time when the output currentcommand value Iout* is not gradually increasing or not graduallydecreasing, the input current amplitude command value creation means 50applies proportional integral (PI) control to the difference 31 betweenthe DC voltage Vdc and the voltage target value Vdc* and then outputsthe value, as the input current amplitude command value IinAMP*. Thefollowing control until the gate signal 37 is outputted to thesemiconductor switching device 7 is the same as that at a time when theoutput current command value Iout* is not gradually increasing or notgradually decreasing.

In addition, in order to satisfy the withstanding voltage specificationof the smoothing capacitor 2, the threshold value Vdc th is set to avalue smaller than the withstanding voltage of the smoothing capacitor2. As a result, it is made possible that the input current amplitudecommand value IinAMP* gradually increases in accordance with the outputcurrent command value Iout* and that the DC voltage Vdc, which is thevoltage of the smoothing capacitor 2, is suppressed to be the same as orsmaller than Vdc_th; thus, it is made possible to stably control thevoltage of the smoothing capacitor 2 and the input and output currentsof the electric-power conversion apparatus 1000.

The method of controlling the second electric-power conversion circuit200 is the same as that in Embodiment 1.

In Embodiment 2, there has been described an example in which the secondcharging target value Iout_ref2 is larger than the first charging targetvalue Iout_ref1 and the output current command value Iout* graduallyincreases; however, the foregoing method can be applied also to the casewhere the second charging target value Iout_ref2 is smaller than thefirst charging target value Iout_ref1 and the output current commandvalue Iout* gradually decreases. Even in this case, it is not requiredthat the input current amplitude command value creation means 50utilizes the DC voltage Vdc of the smoothing capacitor 2, detected bythe DC voltage detection circuit 22, in the calculation for creating theinput current amplitude command value IinAMP*. In other words, becausethe input current amplitude command value IinAMP* is created based onthe output voltage Vout, which is equal to the voltage of thehigh-voltage battery 3 and whose temporal change is small, the inputvoltage amplitude VinAMP, which is supplied from an electric-powersystem, the present output current command value Iout*, and theelectric-power conversion efficiency, which is a constant, the effect ofa control delay, caused, for example, by detecting the DC voltage Vdcand AD-converting the detection value, can be eliminated. Therefore,because the input current amplitude command value IinAMP* that isnecessary for the output current lout to follow the output currentcommand value Iout* is appropriately created, it is made possible tosuppress the voltage of the smoothing capacitor 2 from decreasing, toshorten the time until the electric-power supplying operation becomessteady, and to shorten the time for charging the high-voltage battery 3.

Embodiment 3

Next, an electric-power conversion apparatus according to Embodiment 3will be explained. The configuration of the electric-power conversionapparatus according to Embodiment 3 is the same as that of Embodiment 1,represented in FIGS. 1 and 2. By use of FIG. 6, there will be explainedthe control by the control unit 4 and the input current amplitudecommand value creation means 50 in Embodiment 3, especially, theoperation of the input current amplitude command value creation means 50at a time when the electric-power conversion operation is started andthe output current command value is gradually increasing. FIG. 6 is aset of waveform charts for explaining the operation of the firstelectric-power conversion circuit in the electric-power conversionapparatus according to Embodiment 3; the ordinate denotes the outputcurrent, the output-current difference, and the input current, and theabscissa denotes the time t.

At first, in the time period where t<t5 in FIG. 6, the output currentcommand value change determination unit 51 in the input currentamplitude command value creation means 50 detects a change in the outputcurrent command value Iout* after the electric-power conversionoperation has been started and determines whether or not the absolutevalue (equal to the instantaneous value of the Iout*, in Embodiment 3)of a changing amount of the output current command value Iout* from thevalue (“0”, in Embodiment 3) of the output current command value Iout*at a time prior to the start of gradual increase is larger than “0” andsmaller than a threshold value Iout* th that is smaller than theabsolute value (equal to the charging target value, in Embodiment 3) ofthe difference between the output current command value Iout* (“0”, inEmbodiment 1) at a time prior to the start of gradual increase and thecharging target value or

whether or not the absolute value Idiff of the difference between theoutput current command value Iout* and an output current lout is largerthan “0” and larger than a threshold value Idiff_th that is smaller thanthe absolute value (equal to the charging target value, in Embodiment 3)of the difference between the output current command value Iout* (“0”,in Embodiment 3) at a time prior to the start of gradual increase andthe charging target value.

The condition in this case is given by the following equation.

|Iout*−Iout* at a time prior to the start of gradual increase|<Iout*_th

where 0<Iout*_th<|the charging target value−Iout* at a time prior to thestart of gradual increase|or

|Iout*−Iout|=Idiff>Idiff_th

where 0<Idiff_th<|the charging target value−Iout* at a time prior to thestart of gradual increase|.

In this situation, as represented in FIG. 2, the multiplier 52 in theinput current amplitude command value creation means 50 obtains themultiplication product of the output current command value Iout* and theoutput voltage Vout detected by the output voltage detection circuit 24so as to calculate the output electric power Pout at the output currentcommand value Iout*. Then, as the input current amplitude command valueIinAMP*, the input current amplitude command value creation means 50outputs a value, given by the equation below, that is obtained bydividing the output electric power Pout by an input voltage amplitudeVinAMP detected from the input voltage Vin by the control unit 4 and theelectric-power conversion efficiency, of the electric-power conversionapparatus 1000, that is preliminarily stored in the input currentamplitude command value creation means 50 and is based on the conditiondetermined by the output electric power Pout and the input voltageamplitude VinAMP.

IinAMP*=(Iout*×Vout)/(VinAMP×electric-power conversion efficiency)

In this situation, the input current amplitude command value creationmeans 50 stops the processing of applying proportional integral (PI)control to the difference 31 between the voltage target value Vdc* andthe DC voltage Vdc and then resets the output value of the proportionalintegral (PI) control. The following control until the gate signal 37 isoutputted to the semiconductor switching device 7 is the same as that inEmbodiment 1.

In Embodiment 3, it is not required that the input current amplitudecommand value creation means 50 utilizes the DC voltage Vdc of thesmoothing capacitor 2, detected by the DC voltage detection circuit 22,in the creation of the input current amplitude command value IinAMP*. Inother words, because the input current amplitude command value IinAMP*is created based on the output voltage Vout, which is equal to thevoltage of the high-voltage battery 3 and whose temporal change issmall, the input voltage amplitude VinAMP, which is supplied from anelectric-power system, the present output current command value Iout*,and the electric-power conversion efficiency, which is a constant, theeffect of a control delay, caused, for example, by detecting the DCvoltage Vdc and AD-converting the detection value, can be eliminated.Therefore, because the input current amplitude command value IinAMP*that is necessary for the output current lout to follow the outputcurrent command value Iout* is appropriately created, it is madepossible to suppress the voltage of the smoothing capacitor 2 fromdecreasing, to shorten the time until the electric-power supplyingoperation becomes steady, and to shorten the time for charging thehigh-voltage battery 3.

The control of the second electric-power conversion circuit 200 is thesame as that in Embodiment 1.

Next, in the time period where t≥t5 in FIG. 6, before the output currentcommand value Iout* reaches the charging target value, the input currentamplitude command value IinAMP* created as described above becomes thesame as or larger than a preliminarily set upper limit value IinAMP* thof the input current amplitude command value IinAMP*, due to restrictionfrom an input electric-power system side. The condition in this case isgiven by the following equation.

IinAMP*≥IinAMP*_th

In this situation, the input current amplitude command value creationmeans 50 sets the input current amplitude command value IinAMP* toIinAMP*_th (IinAMP*=IinAMP*_th) and then outputs IinAMP*_th.

Here, the method in which the control unit 4 controls the secondelectric-power conversion circuit 200 will be explained by use of FIG.7. FIG. 7 is an explanatory diagram for explaining the operation of thesecond electric-power conversion circuit in the electric-powerconversion apparatus according to Embodiment 3. When an output currentcommand value switching determination unit 54 determines thatIinAMP*≥IinAMP*_th, the control unit 4 stops the processing of graduallyincreasing the output current command value Iout* for the chargingtarget value, applies proportional integral (PI) control to thedifference 31 between the DC voltage Vdc and the voltage target valueVdc* of the smoothing capacitor 2, and then outputs the output, as theoutput current command value Iout*.

As described above, as the output current command value Iout* graduallyincreases, the input current amplitude command value IinAMP* alsogradually increases; as a result, input current amplitude command valueIinAMP* reaches the upper limit value IinAMP*_th of the input currentcommand value; after that, the control unit 4 stops the output currentcommand value Iout* from gradually increasing and then operates theoutput current command value Iout* in such a way that the voltage of thesmoothing capacitor 2 follows the target value. Accordingly, even inthis case, it is made possible that the voltage of the smoothingcapacitor 2 and the input and output currents of the electric-powerconversion apparatus 1000 are stably controlled. That is to say, it ismade possible to suppress the voltage of the smoothing capacitor 2 fromdecreasing and to shorten the time until the electric-power supplyingoperation becomes steady.

In each of foregoing Embodiments 1 through 3, when the created inputcurrent amplitude command value exceeds the upper limit value of theinput current amplitude command value, the input current amplitudecommand value creation means limits the input current amplitude commandvalue to the foregoing upper limit value.

In each of Embodiments 1 through 3, there has been described an examplein which the output current command value Iout* gradually increases orgradually decreases; however, the present disclosure is not limitedthereto but can be applied to the case where the output current commandvalue Iout* changes; thus, the same effect can be obtained.

Although the present disclosure describes exemplary Embodiments 1through 3, it should be understood that the various features, aspectsand functions described in these embodiments are not limited toapplication in the particular embodiment, but instead can be applied,alone or in various combinations to one or more of the embodiments.Therefore, an infinite number of unexemplified variant examples areconceivable within the range of the technology disclosed in the presentapplication. For example, there are included the case where at least oneconstituent element is modified, added, or omitted and the case where atleast one constituent element is extracted and then combined withconstituent elements of other embodiments.

1. An electric-power conversion apparatus comprising: a firstelectric-power conversion circuit that converts electric power of apower source supplied from an input side of the first electric-powerconversion circuit into first electric power and then outputs the firstelectric power from an output side of the first electric-powerconversion circuit; a smoothing capacitor connected with the output sideof the first electric-power conversion circuit; a second electric-powerconversion circuit that converts electric power inputted to an inputside of the second electric-power conversion circuit by way of thesmoothing capacitor into second electric power and then supplieselectric power based on the second electric power to a load connectedwith an output side of the second electric-power conversion circuit; anda controller that controls the first electric-power conversion circuitand the second electric-power conversion circuit so that a voltageacross the smoothing capacitor follows a voltage target value, whereinthe controller has an input current amplitude command value creator thatcreates an input current amplitude command value, which is an amplitudecommand value of an input current of the first electric-power conversioncircuit, in accordance with an output current command value, which is acommand value of an output current of the second electric-powerconversion circuit, when the output current command value changes,wherein based on the input current amplitude command value created bythe input current amplitude command value creator, the control unitcreates an input current command value, which is a command value of aninput current of the first electric-power conversion circuit, whereinthe controller controls the first electric-power conversion circuit sothat an input current of the first electric-power conversion circuitfollows the input current command value, and wherein the controllercontrols the second electric-power conversion circuit so that an outputcurrent of the second electric-power conversion circuit follows theoutput current command value.
 2. The electric-power conversion apparatusaccording to claim 1, wherein when at a starting time of electric-powerconversion operation, the output current command value is changing in anincreasing manner, the input current amplitude command value creatorcreates the input current amplitude command value in accordance with theoutput current command value.
 3. The electric-power conversion apparatusaccording to claim 1, wherein when can absolute value of a differencebetween the output current command value and an output current of thesecond electric-power conversion circuit is the same as or larger than afirst threshold value, the input current amplitude command value creatorcreates the input current amplitude command value in accordance with theoutput current command value.
 4. The electric-power conversion apparatusaccording to claim 1, wherein the input current amplitude command valuecreator creates the input current amplitude command value in accordancewith output electric power obtained from an output voltage of the secondelectric-power conversion circuit and the output current command valueand with an input voltage of the first electric-power conversioncircuit.
 5. The electric-power conversion apparatus according to claim2, wherein the input current amplitude command value creator creates theinput current amplitude command value in accordance with output electricpower obtained from an output voltage of the second electric-powerconversion circuit and the output current command value and with aninput voltage of the first electric-power conversion circuit.
 6. Theelectric-power conversion apparatus according to claim 3, wherein theinput current amplitude command value creator creates the input currentamplitude command value in accordance with output electric powerobtained from an output voltage of the second electric-power conversioncircuit and the output current command value and with an input voltageof the first electric-power conversion circuit.
 7. The electric-powerconversion apparatus according to claim 4, wherein the input currentamplitude command value creator stores an electric-power conversionefficiency, of the electric-power conversion apparatus, that correspondsto the output electric power and the input voltage, and creates theinput current amplitude command value, based on a value obtained bydividing a value of the output electric power by a multiplicationproduct of a value of the input voltage and a value of theelectric-power conversion efficiency.
 8. The electric-power conversionapparatus according to claim 5, wherein the input current amplitudecommand value creator stores an electric-power conversion efficiency, ofthe electric-power conversion apparatus, that corresponds to the outputelectric power and the input voltage, and creates the input currentamplitude command value, based on a value obtained by dividing a valueof the output electric power by a multiplication product of a value ofthe input voltage and a value of the electric-power conversionefficiency.
 9. The electric-power conversion apparatus according toclaim 6, wherein the input current amplitude command value creatorstores an electric-power conversion efficiency, of the electric-powerconversion apparatus, that corresponds to the output electric power andthe input voltage, and creates the input current amplitude commandvalue, based on a value obtained by dividing a value of the outputelectric power by a multiplication product of a value of the inputvoltage and a value of the electric-power conversion efficiency.
 10. Theelectric-power conversion apparatus according to claim 1, wherein whencan absolute value of a difference between the output current commandvalue and an output current of the second electric-power conversioncircuit is the same as or smaller than a second threshold value and anabsolute value of a changing amount of the output current command valuefrom the output current command value at a time before the outputcurrent command value starts to change is the same as or larger than athird threshold value, the input current amplitude command value creatorcreates the input current amplitude command value in such a way that thevoltage across the smoothing capacitor follows the voltage target value.11. The electric-power conversion apparatus according to claim 2,wherein when an absolute value of a difference between the outputcurrent command value and an output current of the second electric-powerconversion circuit is the same as or smaller than a second thresholdvalue and an absolute value of a changing amount of the output currentcommand value from the output current command value at a time before theoutput current command value starts to change is the same as or largerthan a third threshold value, the input current amplitude command valuecreator creates the input current amplitude command value in such a waythat the voltage across the smoothing capacitor follows the voltagetarget value.
 12. The electric-power conversion apparatus according toclaim 3, wherein when the absolute value of the difference between theoutput current command value and the output current of the secondelectric-power conversion circuit is the same as or smaller than asecond threshold value and the absolute value of a changing amount ofthe output current command value from the output current command valueat a time before the output current command value starts to change isthe same as or larger than a third threshold value, the input currentamplitude command value creator creates the input current amplitudecommand value in such a way that the voltage across the smoothingcapacitor follows the voltage target value.
 13. The electric-powerconversion apparatus according to claim 1, wherein when the voltageacross the smoothing capacitor is the same as or larger than a fourththreshold value set to be the same as or larger than the voltage targetvalue, the input current amplitude command value creator creates theinput current amplitude command value in such a way that the voltageacross the smoothing capacitor follows the voltage target value.
 14. Theelectric-power conversion apparatus according to claim 2, wherein whenthe voltage across the smoothing capacitor is the same as or larger thana fourth threshold value set to be the same as or larger than thevoltage target value, the input current amplitude command value creatorcreates the input current amplitude command value in such a way that thevoltage across the smoothing capacitor follows the voltage target value.15. The electric-power conversion apparatus according to claim 3,wherein when the voltage across the smoothing capacitor is the same asor larger than a fourth threshold value set to be the same as or largerthan the voltage target value, the input current amplitude command valuecreator creates the input current amplitude command value in such a waythat the voltage across the smoothing capacitor follows the voltagetarget value.
 16. The electric-power conversion apparatus according toclaim 10, wherein when creating the input current amplitude commandvalue in such a way that the voltage across the smoothing capacitorfollows the voltage target value, the input current amplitude commandvalue creator sets, as an initial value of the input current amplitudecommand value, an input current amplitude command value createdimmediately before the input current amplitude command value is created.17. The electric-power conversion apparatus according to claim 13,wherein when creating the input current amplitude command value in sucha way that the voltage across the smoothing capacitor follows thevoltage target value, the input current amplitude command value creatorsets, as an initial value of the input current amplitude command value,an input current amplitude command value created immediately before theinput current amplitude command value is created.
 18. The electric-powerconversion apparatus according to claim 1, wherein when the createdinput current amplitude command value exceeds an upper limit value of aninput current amplitude command value, the input current amplitudecommand value creator limits the input current amplitude command valueto the upper limit value, and wherein the controller creates the outputcurrent command value of the second electric-power conversion circuit insuch a way that the voltage across the smoothing capacitor follows thevoltage target value.
 19. The electric-power conversion apparatusaccording to claim 2, wherein when the created input current amplitudecommand value exceeds an upper limit value of an input current amplitudecommand value, the input current amplitude command value creator limitsthe input current amplitude command value to the upper limit value, andwherein the controller creates the output current command value of thesecond electric-power conversion circuit in such a way that the voltageacross the smoothing capacitor follows the voltage target value.
 20. Theelectric-power conversion apparatus according to claim 3, wherein whenthe created input current amplitude command value exceeds an upper limitvalue of an input current amplitude command value, the input currentamplitude command value creator limits the input current amplitudecommand value to the upper limit value, and wherein the controllercreates the output current command value of the second electric-powerconversion circuit in such a way that the voltage across the smoothingcapacitor follows the voltage target value.